The present invention relates generally to the field of road construction, including the paving of surfaces, such as roads and the like with road forming mixtures such as asphalt and similar materials, and more particularly to new and improved methods and sensing apparatus for use with road construction equipment wherever the road construction equipment or an element of such road construction equipment is desired to be maintained in a constant relationship to an edge. The road construction may be employed for performing various functions such as paving, cutting and milling, grading, and the laying of such road forming mixtures in a desired location with respect to an edge such as, for example, a curb, the vertical cut edge or the sloping edge of an existing pavement structure, or with respect to the vertical edges of trenches cut in such pavement structures, and similar situations.
Although the methods and apparatus of the present invention are applicable to any situation wherein it is desired to position the road construction equipment or apparatus (or an element of such construction equipment or apparatus, such as the spreading element of a paver, the cutter element of a pavement milling apparatus, or the like) at a desired location with respect to a selected edge of a pavement structure (or in maintaining it in a constant relationship to an edge), such as in laying a new lane of pavement, laying a pavement extension, back-filling a pavement structure, cutting trenches, milling a pavement structure, filling cut-out trenches, and the like, it is particularly useful for consistently producing high density, long-lasting longitudinal joints between a first cold mat section of compacted paving material and a second mat section of fresh paving material, and will be described in detail in that connection. Further, the invention provides new and improved methods and sensing apparatus for increasing the accuracy of laying fresh paving material parallel to, and contiguous with, an edge of a pavement structure.
In the specification and claims hereof, the following terms will be used from time to time and their respective meanings are set forth below for convenient reference:
(1) The term "edge line" means an edge or reference the location of which is to be sensed or determined and includes, but is not limited to, an edge of an existing pavement structure, such as a curb, one or both edges of a trench, the edge of a reference beam or wire, the top inboard edge of a previously laid, compacted and rolled first mat section of cold paving material which forms the longitudinal joint with the joint edge of the second mat section of freshly laid hot paving material. PA1 (2) The term "joint edge" means the edge of fresh paving material which is to be laid at a desired location with respect a selected edge line. PA1 (3) The term "joint end" means the end of a machine element, such as the end of the main screed of a paver, or the end of the extendible screed section of a paver, which is disposed alongside the longitudinal joint during the paving operation. PA1 (4) The term "edge region" means the region which commences at the edge line of a rolled and compacted pavement structure and extends downward from such edge line toward the base or substrate upon which the paving material is laid. PA1 (5) The term "road construction equipment" is used in its broadest sense and is intended to include any road construction equipment or apparatus used or useful in performing the various functions desired in the construction of roadways, such as for example, pavers, paver/finishers, pavement cutting and milling apparatus, and related equipment and apparatus which in operation is desired to be maintained in a constant relationship to a selected reference or edge. PA1 1. Laying the second mat section of fresh paving material parallel to, and contiguous with, the edge of the first mat section, and PA1 2. Providing the second mat section of fresh paving material with sufficient additional fresh paving material to insure that design density is obtained at the longitudinal joint region.
The present invention may be employed with the well known over-lap paving technique or the new and improved paving techniques of my previous U.S. Pat. Nos. 5,051,026 and 5,088,854, and the continuation-in-part application Ser. No. 762,925, now U.S. Pat. No. 5,213,442 Filed Sep. 19, 1991, wherein there are described and claimed new and improved paving methods and apparatus. The descriptions of my foregoing U.S. Pat. Nos. 5,051,026 and 5,088,854, and application Ser. No. 762,925 now U.S. Pat. No. 5,213,442 are incorporated herein by reference.
For example, in accordance with my U.S. Pat. No. 5,088,854, methods and apparatus are provided for producing improved high density , long-life longitudinal joints between a first previously laid mat section of cold paving material and a second mat section of fresh paving material. Briefly, as described in such patent the second mat section of fresh paving material is provided with a quantity of additional fresh paving material formed into a shaped charge of predetermined profile and disposed near the joint edge of the second mat section. The quantity of additional paving material contained in the shaped charge and the configuration of the shaped charge are made such that after rolling, the lateral and transverse compaction forces generated, force sufficient fresh paving material into the joint region to bring the density of the paving material in such joint region to substantially the specified density and substantially the same as that of the first and second mat sections. That is, the resulting density of the entire paved area comprising the two mat sections and the longitudinal joint therebetween is substantially uniform.
As described in my foregoing U.S. Pat. No. 5,088,854, this is accomplished by providing the spreading element of the paver machine, such as the main screed section or an extendible screed/wing section, with a suitable channel or cavity formed in the spreading element which provides for the laying of a region of additional paving material near the joint edge of the second mat section and for forming this additional paving material into a shaped charge having a desired configuration or profile. Extendible screed/wing sections are sometimes also referred to in the art as "end-gates". In known paver machines, the spreading element may include a main screed section and two independent, hydraulically operated, laterally extendible screed sections, one mounted on each end, either in front or in back of the main screed section. Accordingly, the channel or cavity may be formed at one end of the main screed section, or at one end of the extendible screed section. The end of the spreading element in which the shaped charge channel or cavity is formed is the end which will be adjacent the edge line of the first cold mat section when the paver is moved longitudinally alongside the first cold mat section. That is, the cavity will be formed in the joint end of the main screed section, or in the joint end of the extendible screed section.
Briefly, therefore, the requirements for consistently producing such a long-life longitudinal joint are:
Accordingly, in producing such a desired long-life longitudinal joint it is important that the edge of the second mat section of fresh paving material be consistently laid at a selected location with respect to the edge of the first mat section of cold paving material. That is, the joint edge of the second mat section of fresh paving material must be laid so that it has a selected amount of overlap, or so that it is parallel to, and contiguous with, the edge line of the first cold mat section of paving material and in the absence of any overlap.
In the present common over-lap paving practice, the paver finisher machine laying down the second mat of fresh paving material is run about three inches over the edge line of the first mat section of cold paving material to assure that before rolling the joint edge of the second mat section will be contiguous with the edge line of the first cold mat section. For example, it is well known that if the fresh paving material is permitted to lie on top of the first mat section of cold, compacted and rolled paving material, when a conventional multi-wheel roller is run along the joint region, the compacted material of the first mat section supporting one side of the roller will prevent effective compaction of the joint. Accordingly, this fresh paving material should be removed from the top of the first cold mat section before commencing the rolling of the second mat section and the joint region. Removal of this overlap can be accomplished by a workman manually brooming or scraping off the material, providing a scraper bar that is attached to the trailing end of the paver machine, or providing a rotatable brush means attached to the trailing end of the paver machine.